7823
Oxygen Analyser
SENSOR OPERATING TIPS continued
Cross sensitivity with other gases:
Gases or chemicals that will have an influence on the life of the sensor or on the measuring results are:
1.
Combustible Gases
Small amounts of combustible gases will be burned at the hot Pt-electrode surfaces or Al
2
O
3
filters of the sensor.
In general combustion will be stoichiometric as long as enough oxygen is available, the sensor will measure the
residual oxygen pressure which leads to a measurement error. The sensor is not recommended for use in
applications where there are large amounts of combustible gases present and an accurate O
2
measurement is
required.
Investigated gases were:
H
2
(Hydrogen) up to 2%; stoichiometric combustion
CO (Carbon Monoxide) up to 2%; stoichiometric combustion
CH
4
(Methane) up to 2.5%; stoichiometric combustion
NH
3
(Ammonia) up to 1500 ppm; stoichiometric combustion
2.
Heavy Metals
Vapours of metals like Zn (Zinc), Cd (Cadmium), Pb (Lead), Bi (Bismuth) will have an effect on the catalytic
properties of the Pt– electrodes. Exposure to these metal vapours must be avoided.
3.
Halogen and Sulphur Compounds
Small amounts (< 100ppm) of Halogens and/or Sulphur compounds have no effect on the performance of the
oxygen sensor. Higher amounts of these gases will in time cause readout problems or, especially in condensing
atmospheres, corrosion of sensor parts. These gases often outgas from plastic housings and tubes when hot.
Investigated gases were:
Halogens, F
2
(Flourine), Cl
2
(Chlorine)
HCL (Hydrogen Chloride), HF (Hydrogen Fluoride)
SO
2
(Sulphur Dioxide)
H
2
S (Hydrogen Sulphide)
Freons
CS
2
(Carbon Disulfide)
4.
Reducing Atmospheres
Long time exposure to reducing atmospheres may in time impair the catalytic effect of the Pt-electrodes and has
to be avoided. Reducing atmospheres are defined as an atmosphere with very little free oxygen and where
combustible gases are present. In this type of atmosphere oxygen is consumed as the combustible gases are
burned.
5.
Others
Dust. Fine dust (Carbon parts/soot) might cause clogging of the porous stainless steel filter and might
have an effect on the response of the sensor to oxygen changes.
Heavy shocks or vibrations may alter sensor properties resulting in the need for a recalibration.
ECO
line
7823 Oxygen Analyser
E instruments
Page 1
1
of 12
